The present invention relates to a disc drive microactuator system, and more particularly to a sensor for detecting the relative position of a movable portion of a microactuator.
The density of concentric data tracks on magnetic discs continues to increase (that is, the radial spacing between data tracks is decreasing), requiring more precise radial positioning of the head. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuation motor, such as a voice coil motor, to radially position a head on a flexure at the end of the actuator arm. The large-scale motor lacks sufficient resolution to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism, or microactuator, is necessary to accommodate the more densely spaced tracks.
Various microactuator locations and designs have been considered to achieve high resolution head positioning. One promising design involves inserting a silicon-based thin-film structure between the suspension and the slider in the disc drive assembly. One example of a high performance electromagnetic microactuator is disclosed in U.S. application Ser. No. 09/010,100 referenced above, which is hereby incorporated by reference.
It is often important when implementing a dual-stage servo control system for controlling the microactuator to know the relative position of the transducing head as positioned by the microactuator. The position of the microactuator is not necessarily linearly proportional to the signal input to the microactuator transducer, so it is necessary to provide a sensor for detecting the relative position of the microactuator. One example of a position sensor is to implement the microactuator as a dual port device, as shown in the aforementioned Zhang et al. application Ser. No. 09/010,100. The present invention is directed to a position sensing design that is independent of the design of the microactuator transducer.